The overall goal of this project is to purify to homogeneity the two extracellular androgen binding proteins, Testosterone Estradiol Binding Globulin (TeBG) and Androgen Binding Protein (ABP), from rabbit. We will use affinity chromatography and convetional techniques to isolate these proteins. In addition, we will examine their physical and chemical properties and define their immunologic determinants. These studies whould delineate the distinguishing features of ABP which will permit development of a specific radioimmunoassay for this testicular protein in plasma. Since ABP is secreted into blood, this assay will provide a method for assessing testicular function in a species which possess TeBG and ABP. This study will provide an approach to more extensive study in man.